1. Field of the Invention
The present invention relates generally to an acousto-optic modulator, and more particularly, to a multi-channel acousto-optic spatial modulator for fast signal processing by using a plurality of acousto-optic modulating cells connected in a line.
2. Description of the Related Art
One type of conventional multi-channel acousto-optic modulator includes an acousto-optic modulating cell where a plurality of piezoelectric transducers are attached to one surface so that acoustic waves are generated and propagated in parallel with each other. FIG. 1 shows a conventional multi-channel acousto-optic modulator where each channel is constructed by a piezoelectric transducer 22 and an acoustic wave absorber 23 which are both attached to crystal 21 and spaced apart by a constant distance from each other. Signals are applied to the respective channels, and the light is also incident upon each channel at an angle which satisfies the well-known Bragg's angle condition. As the light is transmitted through each channel, it is acousto-optically modulated and processed.
With the conventional multi-channel acousto-optic modulator, the number of displayable pixels is known to be limited to about 2,000, which makes it difficult to employ this type of modulator in an application such as a holographic video system where more than several tens of thousand pixels must be displayed. To overcome the above limitation, light can be acousto-optically modulated by utilizing crystal which has a large aperture in the direction of propagation of the acoustic waves.
A problem however arises when utilizing crystal having a large aperture because it is not easy to manufacture them. Further, since data should be continuously input through a single input end, the time required to input data becomes long and thus it is difficult to input data at a high speed.
Therefore, there is a need for a new multi-channel acousto-optic spatial modulator which can solve the aforementioned problems.